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60th IEEE Vehicular Technology Conference

作者： Garg, D Adachi, F Tohoku Univ Dept Elect & Commun Engn Sendai Miyagi Japan

ISBN: (纸本)0780385217

For high-speed data communications, channel coding and high-level modulation will be inevitable. In this paper, we compare the turbo coded performances of DS-CDMA and MC-CDMA which are the major contenders for next generation wireless signaling technique. Minimum mean square frequency-domain equalization (MMSE-FDE) is assumed for both DS- CDMA and MC-CDMA. The loa-likelihood ratio (LLR) computation is used to generate the soft decision value needed for turbo decoding. It is found that the DS-CDMA performance is the same for all spreading factor (ST) and equivalent to it fully spread MC-CDMA for, all modulation levels and coding rates. For an uncoded system, DS-CDMA is better than MC-CDMA for smaller SF due to a larger frequency diversity gain. However, with turbo coding, MC-CDMA with smaller SF provides better performance due to larger coding gain owing to better frequency interleaving and severe orthogonality destruction for larger SF and DS-CDMA wherein a symbol is spread over the entire bandwidth.

关键词： DS-CDMA MC-CDMA MMSE-FDE MQAM turbo coding

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turbo coded MIMO multiplexing with iterative adaptive soft parallel interference cancellation

Turbo coded MIMO multiplexing with iterative adaptive soft p...

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60th IEEE Vehicular Technology Conference

作者： Nakajima, A Garg, D Adachi, F Tohoku Univ Dept Elect & Commun Engn Sendai Miyagi 980 Japan

ISBN: (纸本)0780385217

Iterative adaptive soft parallel interference canceller (ASPIC) is proposed for turbo coded multiple-input multiple-output (MIMO) multiplexing. ASPIC is applied to transform a MIMO channel into single-input multiple-output (SIMO) channels for maximum ratio diversity combining (MRC). In the iterative ASPIC, replicas of the interference from different transmit antennas are generated and subtracted from the received signals. The log-likelihood ratio (LLR) sequence obtained as the turbo decoder output is fedback for iterative interference cancellation. At the transmitter, the information bit sequences and parity bit sequences are transmitted from different antennas. The achievable bit error rate (BER) performance of the turbo coded MIMO multiplexing with the proposed iterative ASPIC in a Rayleigh fading channel is evaluated by computer simulation.

关键词： MIMO multiplexing iterative ASPIC turbo coding log-likelihood ratio

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turbo equalization receivers for evolved GSM/EDGE radio access network using QAM modulation

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Physical Communication 2008年第3期1卷 229-235页

作者： Nickel, Patrick Gerstacker, Wolfgang Reck, Christoph Koch, Wolfgang University of Erlangen-Nuremberg 91058 Erlangen Cauerstr. 7 Germany University of Erlangen-Nuremberg 91058 Erlangen Cauerstr. 9 Germany

For evolution of the GSM/EDGE radio access network (RAN), the use of higher order modulation like 16- and 32-ary quadrature amplitude modulation (QAM) is considered in standardization for increased peak data rates and reduced transmission delays. In this paper, an optimized receiver design for different packet data transmission schemes is proposed. turbo coding and turbo equalization is discussed for improved power efficiency and interference robustness. An efficient complexity reduction of the equalizer enables the usage of turbo equalization at a complexity comparable to that of separate equalization and decoding for turbo-coded transmission. © 2008 Elsevier B.V. All rights reserved.

关键词： Complexity reduction GSM/EDGE Higher order modulation turbo coding turbo equalization

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Effect of Array Geometry on the Capacity of the turbo-Coded Beamforming Aided Uplink

Effect of Array Geometry on the Capacity of the Turbo-Coded ...

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70th IEEE Vehicular Technology Conference

作者： Sugiura, S. Yang, D. Chen, S. Yang, L. -L. Hanzo, L. Univ Southampton Sch ECS Southampton SO17 1BJ Hants England

ISBN: (纸本)9781424425143

This paper investigates the effect of different array geometries on the performance of the turbo coding assisted beamforming uplink. More specifically, we focus on the maximum achievable rate as a measure of the system performance, which is calculated with the aid of EXIT chart analysis. Our performance results recorded for K = 4 uplink receiver antenna elements at the Base Station (BS) supporting M = 4 or M = 7 users demonstrated that the Hexagonal Array (HA) slightly outperforms the Uniform Linear Array (ULA) and Uniform Circular Array (UCA), when we have a low angular spread sigma for the Direction-Of-Arrival (DOA) of each user. It is also demonstrated that the performance difference becomes smaller upon increasing the angular spread sigma.

关键词： Array geometry beamforming capacity turbo coding

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Low-complexity BCJR decoder for turbo decoders and its VLSI implementation in 0.18-μm CMOS 62

Low-complexity BCJR decoder for turbo decoders and its VLSI ...

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62nd IEEE Vehicular Technology Conference

作者： Sabeti, L Ahmadi, M Tepe, KE Univ Windsor Dept Elect Engn Windsor ON N9B 3P4 Canada

ISBN: (纸本)0780391527

This paper proposes a low-complexity design for BCJR or Maximum a posteriori (MAP) decoders. Max-Log-MAP algorithm, which offers a good compromise between performance and complexity, is selected for implementation. The decoder architecture is parallel and pipeline. New quantization and new branch metric calculation unit are proposed in this paper. Overall decoder design is flexible to the transmission block lengths, which makes it appropriate for variable length transmission systems. Performance results are tested on turbo decoders and show that the proposed BUR decoder is quite suitable for turbo decoders. The chip is implemented in a 0.18-mu m six-layer metal CMOS technology and has the core size of 1mm(2) (including two memories). The throughput of the turbo decoder is 6.5Mb/s after 10 iterations.

关键词： turbo coding Max-Log-MAP algorithm implementation

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Pipelined parallel architectures for high throughput turbo decoding

Pipelined parallel architectures for high throughput turbo d...

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IEEE Asia Pacific Conference on Circuits and Systems

作者： Lou, Xizhong Chen, Yanmin China Jiliang Univ Coll Informat Engn Hangzhou 310018 Peoples R China

ISBN: (纸本)9781424403868

A new pipelined parallel architecture for turbo decoding is presented. It runs at nearly four times the speed of the traditional architecture with tolerable hardware resource increasing. The bottleneck in turbo decoder is the Add-Compare-Select-Offset (ACSO) unit used in forward and backward recursive state metrics (FRSM, BRSM) calculation. In the new architecture the critical path in ACSO unit is divided into four shorter evenly parts by inserting four register vectors, which improves the working frequency of the turbo decoder. And the sliding window architecture is modified to make use of the new ACSO unit. At the same time, the received symbol sequence is divided into four evenly pieces, that are fed into the same ACSO unit one after another to form the pipeline. Then the speed of turbo decoder will be approximately four times as the old one.

关键词： turbo coding ACSO unit sliding window MAP algorithm Log-MAP algorithm

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Adaptive Channel coding to Enhance the Performance in Rayleigh Channel

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INTERNATIONAL JOURNAL OF ADVANCED COMPUTER SCIENCE AND APPLICATIONS 2024年第6期15卷 504-511页

作者： Srividya, L. Sudha, P. N. Dayananda Sagar Coll Engn Dept Elect & Commun Engn Bangalore India KS Inst Technol Dept Elect & Commun Engn Bangalore India

Rayleigh fading channel model is usually used to model real time wireless mobile communication as it has the potential to emulate the multipath scattering effect, dispersion, fading, reflection, refraction and Doppler shift. Mobility and interferences, will change the channel conditions over the time and so will the error environment and results in variable bit error rates (BER). Fixed channel coding schemes have proven in providing reliability of the data despite of poor channel conditions, but fails to contend with time varying channel conditions. Hence they suffer loss in the information rate during good channel conditions. There is need for adaptive scheme that adapts dynamically to channel conditions improving the overall performance and reliability in communication. An adaptive channel coding technique(ACC) is proposed in this paper which requires a simple statistics from the receiver and switches two channel coding schemes dynamically to the changing environment and makes it different from other schemes which deals dynamic tuning of parameters of one Error control coding (ECC) scheme. This strategy not only guarantees reliability but also spectral efficiency as channel capacity is utilized effectively by switching between two ECCs, less robust (high data rate) Convolutional ECC is used when the channel conditions are good and more robust (low data rate) turbo ECC is used when the channel conditions degraded. Proposed concept is implemented using MATLAB and results outperforms the conventional fixed ECC schemes, an effective reduction of Eb/N0 requirement is obtained for a target BER compared to the fixed or predetermined ECCs. ACC is tested under various mobile channel environment and proven resilient to varying channel conditions. It is beneficial in providing flexibility in QoS by changing the switching criteria according to the application.

关键词： Adaptive error control coding turbo coding convolutional coding bit error rate throughput Rayleigh channel

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Methods for carrier synchronization of short packet turbo coded signals

Methods for carrier synchronization of short packet turbo co...

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15th IEEE International Symposium on Personal, Indoor, Mobile, Radio Communications (PIMRC 2004)

作者： Rahamim, Y Freedman, A Reichman, A Tel Aviv Univ Sch Elect Engn IL-69978 Tel Aviv Israel

ISBN: (纸本)0780385233

turbo codes, which provide superior performance, close to the Shannon limit, have found their way into WLAN and mobile system standards. Synchronization of turbo-coded signals operating at low SNR conditions may be difficult, especially for short packet transmission. This paper proposes two techniques for using the turbo decoder information to improve the carrier phase and frequency offset synchronization for short packets communication systems. One of those techniques, which is based on soft-decisions produced by the turbo decoder can be used for tracking. The other technique is based on maximizing a newly invented cost function, the MSSO(Deltaf,phi) function, to acquire and track the carrier frequency and phase errors, with the cost of complexity. A combination of the two techniques is introduced as well to provide a wholesome solution.

关键词： phase and frequency synchronization turbo coding packet radio

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Performance Evaluation of AMC turbo Coded OFDM for 3GPP Long Term Evolution downlink system

Performance Evaluation of AMC turbo Coded OFDM for 3GPP Long...

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International Conference on Multimedia Computing and Systems (ICMCS)

作者： El Makhtari, Salima Moussaoui, Mohamed Samadi, Hassan Ecole Natl Sci Appl Lab Technol Informat & Commun Tangier Morocco

ISBN: (纸本)9781467315203

This paper presents a performance evaluation of OFDM LTE downlink physical layer according to the latest 3GPP specifications. Particularly, adaptive modulation and coding (AMC) is described and analyzed. This is in conjunction with the turbo decoding algorithm Max-Log-Maximum A Posteriori (Max-Log-MAP) used in soft input soft output (SISO) decoders. The performance analysis is carried out in terms of bit error rate (BER) and throughput by varying parameters such as signal to noise ratio (SNR), modulation schemes, coding rates and decoding iterations number.

关键词： 3GPP LTE OFDM turbo coding Adaptive Modulation and coding Throughput BER

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turbo Codification Techniques for Error Control in a Communication Channel

Turbo Codification Techniques for Error Control in a Communi...

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9th Mexican International Conference on Artificial Intelligence (MICAI)

作者： Manrique Ramirez, Pablo Marquez Ramirez, Rafael Antonio Pogrebnyak, Oleksiy Sanchez Fernandez, Luis Pastor Inst Politecn Nacl Ctr Invest Computac Mexico City 07738 DF Mexico

ISBN: (纸本)9783642167607

An implementation of the turbo coding technique for data error detection and correction in data transmission is presented. The turbo coding technique is known to be efficient in data transmission adding redundant parity that provides a high error correction capacity decreasing the number of erroneous bits for low signal to noise ratios increasing the number of iterations. The turbo encoder and turbo decoder were implemented in a FPGA development system. The design is oriented to reach a transmission speed near to the theoretical Shannon's capacity of the communication channel and minimum possible energy consumption using only the FPGA resources without external memories.

关键词： Error correction coding turbo coding FPGA

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